The present invention pertains to pumping apparatus with flexible diaphragms. More specifically the invention relates to support discs for supporting the flexible diaphragm in such apparatus.
In this particular art it is well known to provide a support disc on one side of the pump diaphragm for preventing the diaphragm from being drawn into the pump cylinder wherein the piston undergoes its forward and backward motion. This is in more detail described, for example, in the U.S. Pat. No. 2,345,693, the disclosure of which is incorporated herein by reference.
The support discs are provided with holes to allow the pump liquid to flow freely through the discs and exert a pulsating pressure on the diaphragm under the influence of the backward and forward motion of the piston. The holes usually have a diameter ranging from approximately 3 to 10 millimeters.
However, it is a disadvantage of such a support disc that the diameter of the holes is too large in order to really prevent the diaphragm from becoming damaged, even if such diameter should only be 3 millimeters. The diaphragm which may only be 0.25 millimeters thick may still be drawn inwardly by the piston and may thus be destroyed. This, of course, would lead to a sudden break down of the pump. Replacing the diaphragm would then be both costly and time consuming.
This disadvantage could, of course, be readily overcome by reducing the diameter of the holes to, for example, 0.5 millimeters. However, in order not to disturb the free pulsation of the pump liquid through the disc a great number of 0.5 millimeter holes or slots would have to be provided in the support disc. This, on the other hand, represents a further disadvantage. Drilling a great number of 0.5 millimeter holes through a disc which may well be 2 millimeters thick is very difficult and so is the cutting or milling of 0.5 millimeter wide slots.
It is therefore the object of the invention to provide a support disc having a large number of narrow holes or slots which is still easy to manufacture.